MONDAY, April 6, 2015 (HealthDay News) -- Many people turn to commercial weight-loss programs to help them shed excess pounds, but there's surprisingly little scientific evidence to show whether or not these plans can help keep weight off for the long-term, a new report reveals.
Only two out of 32 major commercial weight-loss programs marketed nationwide -- Weight Watchers and Jenny Craig -- can boast scientific evidence showing their clients maintain weight loss for at least a year, the researchers found.
Most programs haven't received any study at all regarding their effectiveness, or have only been reviewed for short-term success, said lead author Dr. Kimberly Gudzune. She is an assistant professor of medicine and a weight-loss specialist at the Johns Hopkins University School of Medicine in Baltimore.
"We still don't know whether a lot of these programs work," Gudzune said.
The study, which was not funded by any commercial weight-loss plan, is published in the April 7 issue of the Annals of Internal Medicine. Gudzune and several of her co-authors reported receiving support from the U.S. National Heart, Lung, and Blood Institute, and the U.S. National Institute of Diabetes and Digestive and Kidney Diseases.
The obesity crisis prompted the study, as doctors weigh the various options on hand to help their patients lose weight, Gudzune said.
Two-thirds of adults in the United States are overweight or obese, increasing their risk for high blood pressure, heart disease and type 2 diabetes, the study authors pointed out.
In the United States, weight-loss programs were a $2.5 billion business in 2014, with Weight Watchers leading the pack with 45 percent of the market, according to background information in the study. Nutrisystem has about 14 percent of the market, while Jenny Craig has about 13 percent, the study said.
While these plans are popular, doctors don't have a lot of information regarding which show real and sustained results, Gudzune said.
"Because I'm looking for the health benefits associated with sustained weight-loss, I feel more comfortable recommending a program to a patient that's been scientifically proven to work," she said.
Gudzune and her colleagues reviewed 4,200 studies. They were only able to find randomized, controlled trials (considered the "gold-standard" for medical research) for 11 of the 32 major weight-loss programs.
Those programs included Weight Watchers, Jenny Craig, Nutrisystem, Health Management Resources, Medifast, OPTIFAST, Atkins, The Biggest Loser Club, eDiets, Lose It!, and SlimFast.
Of those 11, only Weight Watchers and Jenny Craig had gone through studies showing that people not only lost weight but kept it off for at least a year, researchers found.
Weight Watchers helped participants sustain almost a 3 percent greater weight loss at 12 months than people in a control group who just received information about healthy eating.
Jenny Craig resulted in about a 5 percent greater weight loss after a year, compared with a control group provided nutrition education and counseling, the researchers found.
Another popular program, Nutrisystem, resulted in nearly a 4 percent greater weight loss than a control group. However, the available studies only followed up for three months and could not prove sustained weight loss, according to the report.
The study authors found that very low-calorie diets like Medifast, OPTIFAST and Health Management Resources only appeared to provide short-term results.
"We saw that people seem to lose weight in the short term, but once we got to further time points out it seemed people were regaining the weight they lost," Gudzune said.
Researchers also found mixed results for Internet or smartphone apps like The Biggest Loser Club, eDiets or Lose It!, which they refer to as 'self-directed plans' alongside Slim-Fast and Atkins.
"Some did show promise as far as short-term weight loss, while for others it was unclear whether they worked," Gudzune said. Noting that these plans tend to be more affordable, she recommended that people discuss them with their doctor.
Costs of the programs varied widely from no cost (for Lose It!) up to nearly $700 a month, according to the study. Weight Watchers costs approximately $43 a month. Jenny Craig, which provides replacement meals, averages $570 monthly, the study found. And, Nutrisystem, which also provides replacement meals, averages about $280 a month, the researchers said.
Weight Watchers and Jenny Craig work because they provide structure, counseling and social support for people who want to lose weight, said Jim White, owner and president of Jim White Fitness and Nutrition Studios in Virginia, and a spokesman for the Academy of Nutrition and Dietetics.
"It teaches you balance. It teaches you consistency. It teaches you about changing your lifestyle for the long haul," White said.
The two plans also focus on portion size, which is a crucial lesson for anyone trying to improve their diet and lose weight, said Heather Mangieri, owner of Nutrition CheckUp in Pittsburgh and a spokeswoman for the Academy of Nutrition and Dietetics.
"Weight-loss programs that teach a point system or have some sort of structure in place to show portion size, they take the guesswork out and that makes it easier," Mangieri said.
Dietary guidelines provided by the U.S. Department of Agriculture and the American Heart Association are great, but they don't offer the same sort of structure for people who struggle to adopt better habits, Gudzune said.
"For many people, doing it on their own is not going to work for them," she said. "Thinking about a commercial program that has scientific evidence to back it up is not an unreasonable approach to take."
For more on weight-loss programs, visit the U.S. National Institutes of Health.